The technical field generally relates to hybrid power train systems, and more particularly but not exclusively relates to control of hybrid power train systems operating in a motor vehicle. The introduction of two or more power sources into a power train introduces the possibility of selecting the power source for the load according to which power source is presently at a more optimal operating condition. For example, during a transient load situation, an electric motor may respond more optimally than an internal combustion engine, and the opportunity for the electric motor to manage the transient portion of the load is introduced. However, selecting the device that is more optimal under the present conditions, without considering future operating conditions, introduces the possibility of reaching a system limit—for example running a battery out of charge.
Additionally, certain operations may reduce the service life of components in the system, such as behaviors to save fuel economy that result in rapid cycling of battery charge. Further, the increased number of devices in the system includes an increased number of constraints for those devices that must be considered when coordinating devices to meet the desired output. Certain devices may not be available for full output in certain operating conditions, for example as an electric motor is heated the maximum power output becomes limited.
The optimal operating decisions for the devices also depend upon the duty cycle and operating conditions corresponding to a particular application. In addition, when a component in the system is failed or has a fault, the optimal operating decisions may be significantly different than when all components are operating correctly, but the determination of the new optimum remains complex. Further, a change in a component due to normal usage over time may alter the behaviors that are optimal. For example, if an aged aftertreatment catalyst requires more frequent regeneration events, or the maximum state-of-charge of an aged battery is lower than in a new battery, the optimal behaviors of the hybrid power train may change over time.
Therefore, further technological developments are desirable in this area.